Flashcards in Lecture 34: Photosynthesis-light reactions Deck (10)
what initiates light reactions in photosynthesis?
absorbance of light
consequence of electron transfer reactions in light reactions?
1) production of QH2 or NADPH (NADH)
2)translocate H+ and generate a proton gradient across a membrane-used for ATP synthesis
3)in cyanobacteria and plants, O2 is produced from H20
why is it called Dark reactions
don't require light
Subsequent to the light reactions.... dark reactions...
-biosynthesis that uses the ATP and NADPH to fix CO2 as 3-phosphoglycerate
-3-phosphoglycerate is used then to make C4 to C7 sugars
What wavelength does visible light contain?
700nm (red) to 400 nm (dark blue)
Types of Photosystems
Complex PsI and PSII
PS1 + PSII
-in purple and green filamentous bacteria
-type II reaction center with P870 chlorophyll
-works with cytochrome bc1 complex in a cyclic system
-There is a H+ translocation but not net production of NADPH
-in green sulfur bacteria
-type 1 reaction center with P700 chlorophyll
-works either with cytochrome bc complex in a cyclic system without net production of NADPH
with an electron done such as H2S or S2O32- with net production of NADPH
Complex PSI + PSII
-photosystems act in series
-works with cytochrome bf complex
-organisms use H2O as source of electrons to reduce the primary pigment in PSII with a net production of NADPH